Mapping of multiple muscles with transcranial magnetic stimulation: absolute and relative test-retest reliability.

The spatial accuracy of transcranial magnetic stimulation (TMS) may be as small as a few millimeters. Despite such great potential, navigated TMS (nTMS) mapping is still underused for the assessment of motor plasticity, particularly in clinical settings. Here, we investigate the within-limb somatotopy gradient as well as absolute and relative reliability of three hand muscle cortical representations (MCRs) using a comprehensive grid-based sulcus-informed nTMS motor mapping. We enrolled 22 young healthy male volunteers. Two nTMS mapping sessions were separated by 5-10 days. Motor evoked potentials were obtained from abductor pollicis brevis (APB), abductor digiti minimi, and extensor digitorum communis. In addition to individual MRI-based analysis, we studied normalized MNI MCRs. For the reliability assessment, we calculated intraclass correlation and the smallest detectable change. Our results revealed a somatotopy gradient reflected by APB MCR having the most lateral location. Reliability analysis showed that the commonly used metrics of MCRs, such as areas, volumes, centers of gravity (COGs), and hotspots had a high relative and low absolute reliability for all three muscles. For within-limb TMS somatotopy, the most common metrics such as the shifts between MCR COGs and hotspots had poor relative reliability. However, overlaps between different muscle MCRs were highly reliable. We, thus, provide novel evidence that inter-muscle MCR interaction can be reliably traced using MCR overlaps while shifts between the COGs and hotspots of different MCRs are not suitable for this purpose. Our results have implications for the interpretation of nTMS motor mapping results in healthy subjects and patients with neurological conditions.

Brain-Derived Neurotrophic Factor in Patients with Primary Open-Angle Glaucoma and Age-related Cataract.

PURPOSE: To study brain-derived neurotrophic factor (BDNF) content in aqueous humor (AH), lacrimal fluid (LF), and blood serum (BS) in patients with age-related cataract and primary open-angle glaucoma (POAG). METHODS: BDNF was studied in 57 patients with age-related cataract, 55 patients with POAG combined with cataract, and 29 healthy controls (one eye in each person). AH was sampled during cataract surgery. RESULTS: The levels of BDNF in LF and BS did not differ in cataract patients and controls. The concentration of BDNF (pg/mL) in patients with POAG and cataract was lower than in cataract patients in AH (35.2 ± 14.2 vs. 54.6 ± 29.6, P < 0.001), LF (78.0 ± 25.1 vs. 116.2 ± 43.1, P < 0.001), and BS (19230 ± 5960 vs. 22440 ± 7580, P < 0.02), while the AH/LF ratio was similar (0.46 ± 0.18 vs. 0.48 ± 0.19). The AH level of BDNF declined in early POAG and relatively increased in the next stages of the disease, inversely correlating with visual field index (Pearson's correlation coefficient r = -0.404, P = 0.002) and average retinal nerve fiber layer thickness (r = -0.322, P = 0.018). BDNF contents in LF and BS were also the lowest in early POAG. BDNF in AH strongly correlated with its content in LF (r = 0.66, P < 0.000). A formula was suggested to calculate the AH concentration of BDNF basing on its content in LF. CONCLUSIONS: BDNF contents are decreased in AH, LF, and BS of patients with POAG demonstrating a significant decrease in the early POAG and relative increase in the next stages of the disease. A strong correlation exists between BDNF contents in AH and LF.

Ciliary neurotrophic factor in patients with primary open-angle glaucoma and age-related cataract.

Purpose: To study the ciliary neurotrophic factor (CNTF) concentration in the aqueous humor (AH), lacrimal fluid (LF), and blood serum (BS) in patients with age-related cataract and primary open-angle glaucoma (POAG). Methods: CNTF concentrations were studied in 61 patients with age-related cataract, 55 patients with POAG combined with cataract, and 29 healthy controls (one eye in each person). Preliminary experiments permitted us to extend the minimum quantifiable value of the CNTF Quantikine enzyme-linked immunosorbent assay (ELISA) kit to 2.5 pg/ml. Results: The levels of CNTF in LF and BS did not differ in patients with cataract and controls. The CNTF concentration (pg/ml) in patients with POAG and cataract was lower than in patients with cataract (p<0.001) in AH (39.9±26.2 versus 57.2±25.6) and in LF (25.7±14.9 versus 39.9±18.0). The differences were not statistically significant for the CNTF level in BS (5.45±4.72 versus 5.96±4.92) and the AH/LF ratio (1.69±1.05 versus 1.58±0.70). In the patients with POAG, the AH level of CNTF correlated with the visual field index (Pearson's correlation coefficient r = 0.35, p = 0.01). A statistically significant decrease in the AH and LF concentrations of CNTF was observed in patients in all stages of POAG compared with the cataract group. This decrease was particularly prominent in patients with severe glaucoma. Compared to patients with combined early and moderate stages of disease patients with advanced glaucoma showed an insignificant reduction in the median CNTF concentration in AH and LF. The serum CNTF concentration did not show any dependence on the glaucoma stage. The CNTF concentration in the AH strongly correlated with the CNTF concentration in the LF (r=0.71, p<0.000). A formula was suggested to calculate the concentration of CNTF in AH based on the CNTF concentration in LF. Conclusions: The CNTF concentration is reduced in the AH and LF of patients with POAG, especially in those with severe visual field loss. The CNTF concentration in AH and LF showed a strong correlation, and this phenomenon opens up new options for a noninvasive estimation of the CNTF concentration in AH. The CNTF concentration established in the AH, LF, and BS of patients with age-related cataract can serve as normative data for persons older than 50 years old.